Re: Camera Gamut (was Re: basiccolor INPUT)
Re: Camera Gamut (was Re: basiccolor INPUT)
- Subject: Re: Camera Gamut (was Re: basiccolor INPUT)
- From: Tom Lianza <email@hidden>
- Date: Mon, 07 Nov 2011 19:05:54 -0400
- Thread-topic: Camera Gamut (was Re: basiccolor INPUT)
To all,
By definition, if the camera has overlapping filter sets, all wavelengths
will be captured and unless there is a horrible problem in post processing,
energy from very small shifts in wavelength will be quite measureable.
That's how we measure the spectral sensitivity of a sensor.
The earlier paper that was cited, written, by Jack Holms showed the
effective difference between the outline of the locus produced by CIE 1931
observer and an arbitrary camera. That locus is often mistakenly stated to
represent a gamut. It does not. It is true, particularly with emissive
narrow band radiation, that a camera may not be able to capture the entire
wavelength range at one setting of exposure, but it certainly will be able
to distinguish the difference between two wavelengths very close together.
After all, the human eye does the same thing with three overlapping
sensitivities.
The issue, as Brill correctly stated, isn't gamut, it is how colors are
arbitrarily mapped by the continuous sensitivities of the camera. The real
question comes down to a decision to get the most accurate color or the most
pleasing color, which has nothing to due with gamut. In general, gamut
clipping occurs in all cameras using a predetermined color space, because
the clipping is defined by the selected color space, typically sRGB or Adobe
RGB. The camera certainly captures data outside of these spaces (assuming
that the sensitivities are reasonable). In raw processing, the color space
is often assumed to be RIMM (or ProPhoto RGB)which is defined with imaginary
color primaries and it far exceeds the gamut of real world colors, but it
does not enclose the CIE locus.
I'm not sure that using hyperbole such as "the contiguous zone, outside of
which the device cannot continue to distinguish color differences in a
meaningful way", really adds to a serious technical discussion of the issue
and continuing to define one word, used in an incorrect context, with a
vague description adds nothing to the end user's understanding of the
issues.
End user's are quite capable of understanding complex issues, if those
issues are explained properly. The trick is in the teaching, not the hype.
Regards,
Tom Lianza
On 11/7/11 7:25 PM, "Charles D Tobie" <email@hidden> wrote:
> I can't resist commenting that the extensive quoting of Dr. Brill is the most
> coverage Datacolor has received on this list in a long while. As a friend and
> colleague of Mike I respect his comments, but I don't believe his proposal is
> the one end users are looking for. Actually, describing the needs and views of
> the end user to Mike is one of my main roles with him.
>
> My suggestion would be that the gamut of a color capture device be considered
> "the contiguous zone, outside of which the device cannot continue to
> distinguish color differences in a meaningful way", specifically further
> increases in saturation. If a capture device can continue to effectively
> distinguish color without changing settings on the device, then it's "gamut
> limit" has not yet been reached. This simple concept can then be appended with
> most everything else that as been said here, but the end user is unlikely to
> take away much from these further complications. Color scientists, on the
> other hand, will.
>
> C. David Tobie
> Global Product Technology Manager
> Imaging Color Solutions
> Datacolor inc.
> email@hidden
> www.datacolor.com
>
> On Nov 7, 2011, at 5:03 PM, Richard Wagner <email@hidden> wrote:
>
>>
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